Production of chlorinated methyl naphthalenes



Patented Oct. 2, 1951 PRODUCTION OF CHLORINATED METHYL NAPHTHALENES Herbert Stanislaus Boyd-Barrett, .Sale, James Ronald Holker, Monton,and Herbert Steiner,

Eccles, England, ,assignors to Petrocarbon Lim ited, London, England i 1.

' No Drawing. Application February 24, 1948, Se-, I

rial No. 10,566. In Great Britain February 24,

This invention relates to the production of side-chain chlorinated methyl naphthalenes, that is methylnaphthalenes having a chlorine atom substituted in the side-chain.

It is known that vapour phase chlorinations of mono-cyclic aromatic hydrocarbon containing methyl groups, may give substitution of hydrogen or the methyl group. For instance, with toluene, U. S. Patent No. 1,246,739, Gibbs and Geiger, 1917, and British Patent No. 378,866, T. S. Wheeler, November 8, 1932, side-chain chlorination takes place at temperatures above 250 C. with or without presence of ultra-violet light and in the absence of specific catalysts or chlorine carriers. Similar products are obtained from toluene in the liquid phase at temperatures near the boiling point, and in direct sunlight.

It i stated in Side-chain chlorination of arcmatic compounds in the vapour phase by G. V. Asolkar and P. C. Guha, Journal of the Indian Chemical Society, February, 1946, that in the vapour phase, the chlorination of toluene yields very good results (about 85% conversion) yielding benzyl chloride. This is said to be a better way of chlorinating toluene in the side-chain than the usual method of chlorinating in the liquid phase. The chlorination of the nitro-toluenes in the vapour phase was also expected to proceed in the side-chain especially in the case of the metaand para-compounds. The ortho-compound may not be chlorinated because of the steric hindrance of the nitro group in the compound. The side-chain chlorination of the metaand para-compounds has been carried out in the liquid phase (Hanssermann and Beck, Ber., 1892, 25, 2445) but the results are negative in the vapour phase even after prolonged chlorination.

It appears, therefore, that the presence of cer- .tain substituents in the ring may affect the chlorination or hydrogen replacement in the sidechain.

The chlorination of alkylated aromatic compounds containing two or more aromatic rings either condensed or linked, so far has always been carried out in the liquid phase, and has resulted in the production of a large proportion of nuclear substituted chloro-compounds particularly at 10W temperatures. At high temperatures, increased amounts of side-chain derivatives can be obtained from mono-methyl naphthalenes (see Schultze, Ber. 17, 1529; Scherler, Ber. 24, 3930, and Wislicenus and Wren, Ber. 38, 506), but the yields are still unsatisfactory and also large amountsof Earry residues are produced under these condione.

5 Claims. (0]. 260651) The main object of the present invention is to provide a more efficient process for the production of side-chain chlorinated methylnaphthalenes.

The invention consists in a process for the production of side-chain chlorinated methyl naphthalenes in which process chlorine and methyl naphthalene vapour are separately preheated to; and brought into contact with each other at, a temperature between th vaporisation point of the methyl naphthalene and 500 C. and under a pressure which is sub stantially atmospheric or higher up to about 2 atmospheres absolute, the time ofcontact betweenthe'reactantsat the said temperature being notmore than 5 seconds and the chlorine always being present in an amount less than that required stoichiometrically for mono-substitution by chlorine.

The invention also consists in a process in accordance with the preceding paragraph applied for the production of side-chain chlorinated mono-methylnaphthalenes. i The invention also consist in a process: in accordance with either of' the preceding two paragraphs in which the temperature of the reaction is between 300 and 400 C. r l The invention also consists in a process in accordance with any of the preceding three paragraphs in which the time of contact between the reactants is 1 second or less.

The invention alsoconsists in improved processes for the production of side-chain chlorinated methyl naphthalenes and in products which may be made by those processes especially in isolated form.

The following'examples illustrate how the in vention may be carriedinto effect:

a Example I A throughput of mls. (calculated as liquid) per hour of the vapour of a mixture of uand e-methyl naphthalenes preheated to about 300 C. was maintained for 1 hour through a glass reactor, which was filled with glass chips (approximately 50% free space) and surrounded by a furnace which kept the temperature inside the reactor at 300 C. Dry chlorine, preheated to about 300C. Was also fed to the reactor at a rate corresponding to approximately 50% of the amount of chlorine stoichiometrically equivalent to the methyl naphthalenes for mono-substitution. The pressure in the reactor was substantially atmospheric. A contact time of about 5 seconds was allowed, the products leaving the reactor being rapidly cooled by quenching. The

A throughput of 150 mls. (calculated as liquid) 7 per hour of a mixture of the vapour of aand p-methyl naphthalenes (approximately 50% c and 50% preheated to about 300 (1., was maintained for 1 hour through a lass reactor,

consisting of a spiral of 40 cm.straight length and 1.0 cm. internal diameter, kept at 300 C. Dry chlorine preheated to about 300 C. was at the same time fed to the reactoratarate corres spending with approximately of the-amount of chlorine stoichiometrically equivalent to the methyl naphthalenes for mono-substitution. The pressure in the reactor was substantially atmosnh riciA contact time ofBsecondswas allowed. the products being rapidly cooled on leaving the rea tor. The liq id product was leingms. On fractionation this gave 9'7 gms. of unchanged methyl naphthalenesand 5.0 gms. of chlorinated methylnaphthalenes. This represents a conversion of, 7.6% of the .methyl naphthalenes consumed. 85% of thechlorinated products was found to'be substituted in the side-chain.

Example III A throughput of 1,50 mls. (ealculated as. liquidl per hour of-the vapour of a mixture of aand p-methyl' ,naphthalene ,llreheated to about 300 C. was maintainedthrougha glass reactor consisting of a straight tube of .1 cm. bore, kept at 300 C. At the same time dry chlorine preheated to about 300 C. was fed to the reactor at a rate corresponding to approximately50% of the amount ofchlorine .stoichiometrically equivalent to the .methyl naphthalenes for mono-substitution. A contact time of one second was allowed and the products leaving the reactor'wererapidly cooled- In all 232 gms. of methyl naphthalenes were used and the liquid product was 248 gms. On fractionation this gave, 160' gms'uhohanged methyl naphthalenes and 66 gins. oi chlorinated methyl naphthalenes. represents a conversion; of: 74% based on the methylnaphthalenes consumed. 85% of the chlorinated products was found o be. substituted in the. side-chain.

Example IV A throughput of 150 mls. (calculated as liquid) per hour of the vapor of a mixture of aand p-methyl naphthalenes preheated to 380 C. was maintained through a. gjlassreactor, consisting of a straight tube of 1 cm. bore surrounded by a furnace which kept the temperature inside the reactor at 0 0-. At the same time dry chlorine, dilut wi h. an equal volume or nitrog n and preheated to 380 C. was fed to the reactor at a r te corresponding t approximately 0f the amount of. chlorine stoichiometrically quivalent to the methyl naphthalenes for monosub ti ution. A, contact time oi. one second was allowed and the products leaving the reactor were rapidly c oled. In all 2 ems. methyl naphthalenes were consumed. The liquid product, weighed 278 gms. On fractionation this gave 178 gms. of unchanged methyl naphthalenesand 69 gms. of chlorinated methyl naphthalenes.

This represents conversion of 74.5% based on the methyl naphthalenes consumed. Over 90% 4 General It is important to have a very short contact time in order to expose the labilechlorine products for a very'short time only to high temperatures, thereby reducing the amount of decomposition to a minimum. The time of contact is thus preferably kept just above that at which any chlorine comes through unchanged and at high temperatures may be only a fraction of a second. y

The chlorine fed to. the reaction'zone in the process of the invention may be diluted with 7 an inert gas such as nitrogen.

of the chlorinated products was fouhdfito be substituted in the side-chain.

The process of the invention can be arranged to operate continuously and the unattacked methyl naphthalenes may after separation .by fractional distillation be returned to the reactor for further chlorination.

The products leaving the reaction zone are rapidly cooled and are subjected to fractional distillation, the first runnings from which comprise the unattacked methylfnaphthalenes. of boiling range about 115-125 3./ 15 mm. Hg. The chlorinated product distils at about 140-160 C./ 15 mm. Hg in a weight yield of about 70% of the methyl naphthalenes consumed. a

In contradistinction to chlorination in the liquidphase even when carried outat high temperatures in the neighbourhood of the boiling point of the methyl naphthalene, the process of the present invention results in chlorinated products containing a high proportion, for example, between and of a ohlorinatedproduct which is substituted in the side-chain.

The reaction vessel may be made of glass or any chlorine resistant material and mayor may not be packed. v The tarry deposit which settles on the packing and walls of the reactor can easily be removed by oxidation in a current of air at about 500 C. for a shortperiod.

The inventionrmay be applied to methyl naph-. thalenes in general and to aand ,S-mono-methyl naphthalenes in particular.

Chlorinated products of the type claimed are useful intermediates for the production of naphthyl-alcohols, naphthyl-aceti'c-acids'and the like. We. claim:

1. A process for the production of side-chain chlorinated mono-methyl naphthalenes. by. the vapor phase chlorination of methyl naphthalene, which comprises continuously preheating chlorine and vaporized methyl naphthalene separately and to a temperature between the vaporization point of methyl naphthalene at the pressure employed and 500 0., continuously bringing the two vapors into contact with each other at the above temperature under a pressure of between 1 to 2 atmospheres absolute for a'period not. to exceed 5, seconds, and continuously regulating the relative amounts of the two gases so that the amount of chlorine vapor in contact with the methyl naphthalene vapor is always less than the stoichiometric amount required for complete mono-substitution by chlorine of all the methyl naphthalene present, and continuously separating the formed chloromethyl naphthalenes from the unreacted methyl naphthalene by fractional distillation.

2. The process of claim 1 in which the time of contact between the reactants does not exceed 1 second.

3. The process of claim 1 wherein the chlorine gas is diluted with an inert gas before it is pre heated and fed into the reaction zone.

4. The process of claim 1 wherein the chlorine as is diluted with nitrogen before it is preheated and fed into the reaction zone.

5. A process for the production of side-chain chlorinated mono-methyl naphthalenes by the vapor phase chlorination of methyl naphthalene, which comprises continuously preheating chlorine and vaporized methyl naphthalene separately to a temperature between 300 and 400 C., continuously bringing the two vapors into contact with each other at the above temperature under a pressure of between 1 to 2 atmospheres absolute for a period ranging from a fraction of a second to 5 seconds and regulating the relative amounts of the two gases so that the amount of chlorine vapor in contact with the methyl naphthalene vapor is never more than 50% of the stoichoimetric amount required for complete mono-substitution by chlorine of all the methyl naphthalene present, continuously separating the formed chloromethyl naphthalenes from the unreacted methyl naphthalene by fractional distillation and returning the methyl naphthalene to the reactor.

HERBERT STANISLAUS BOYD-BARRETT.

JAMES RONALD HOLKER.

HERBERT STEINER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,146,142 Ellis July 13, 1915 1,202,040 Ellis 1- Oct. 24, 1916 FOREIGN PATENTS Number Country Date 378,866 Great Britain Aug. 16, 1932 OTHER REFERENCES 

1. A PROCESS FOR THE PRODUCTION OF SIDE-CHAIN CHLORINATED MONO-METHYL NAPHTHALENES BY THE VAPOR PHASE CHLORINATION OF METHYL NAPHTHALENE, WHICH COMPRISES CONTINUOUSLY PREHEATING CHLORINE AND VAPORIZED METHYL NAPHTHALENE SEPARATELY AND TO A TEMPERATURE BETWEEN THE VAPORIZATION POINT OF METHYL NAPHTHALENE AT THE PRESSURE EMPLOYED AND 500* C., CONTINUOUSLY BRINGING THE TWO VAPORS INTO CONTACT WITH EACH OTHER AT THE ABOVE TEMPERATURE UNDER A PRESSURE OF BETWEEN 1 TO 2 ATMOSPHERES ABSOLUTE FOR A PERIOD NOT TO EXCEED 5 SECONDS, AND CONTINUOUSLY REGULATING THE RELATIVE AMOUNTS OF THE TWO GASES SO THAT THE AMOUNT OF CHLORINE VAPOR IN CONTACT WITH THE METHYL NAPHTHALENE VAPOR IS ALWAYS LESS THAN THE STOICHIOMETRIC AMOUNT REQUIRED FOR COMPLETE MONO-SUBSTITUTION BY CHLORINE OF ALL THE METHYL NAPHTHALENE PRESENT, AND CONTINUOUSLY SEPARATING THE FORMED CHLOROMETHYL NAPHTHALENES FROM THE UNREACTED METHYL NAPHTHALENE BY FRACTIONAL DISTILLATION. 